The present invention relates to multi-directionally swept beams and also roll-forming apparatus and methods for forming multi-directionally swept beams and structural members, such as can be used as bumper reinforcement beams, vehicle frames, and non-linear structural members. The present invention further relates to beams and structural members made by same. The present invention is not limited to only bumper reinforcement beams and/or vehicle frames, nor is it limited to apparatus and methods for forming/constructing only these components.
Roll-forming can be a particularly cost-effective way of producing elongated beams and structural members (channel-shaped and tubular), since roll-forming is capable of mass-producing high volumes with relatively lower cost tooling and longer lasting tooling (as compared to stamping dies, especially when high-strength materials are being formed that will quickly wear out stamping dies). However, roll-forming has limitations, such as a limited ability to form non-linear products.
Several ways are known for forming sweeps and curved elongated structural members. For example, see Sturrus U.S. Pat. No. 5,092,512, Sturrus U.S. Pat. No. 5,454,504, and Lyons Published Application U.S. 2006/0277960 which disclose ways of imparting a sweep(s) into a continuous beam made of high-strength material, where the beam has a strength and shape suitable for use as a bumper reinforcement beam. However, these processes are limited to forming beams swept to form one-directional concave shapes. These processes are not capable of forming a beam with alternating (back-and-forth) sweeps, where the alternative sweeps are in opposite directions away from a roll-formed centerline.
Notably, the difficulties of consistently sweep-forming beams and structural members into non-linear shapes is greatly increased as the size and bending moment of a structural beam increases, such as when the beam has a tubular cross section of greater than 50 mm×50 mm, and/or when the sheet material has a high strength (e.g., greater than about 60 KSI tensile strength up to 220 KSI tensile strength), and/or when the swept curvature is relatively sharp such as defining a radius of less than 1500 mm, and/or when sheet thicknesses are greater than 2 mm, . . . especially for combinations of the above.